
Flatness-based control (see [1]}, [2]}; and [3]}, [4]}, [5]}) is a model-based approach which has been well received in many industrial domains. See, e.g., [6]} for tower cranes.

Besides being useful in concrete case-studies (see, e.g., [7]}, [8]}, [9]}, [10]}, [11]} for energy management), model-free control in the sense of [12]}, [13]} has already been illustrated in biomedicine ([14]}, [15]}, [16]}) and in bioengineering ([17]}). Note that the terminology “model-free control” has been used many times with different definitions: see [18]} in oncology.

